A printing method, which is capable of using a print substance for printing with the aid of a preferably pulsed and focused energy beam, such as, for example, a laser beam or an electron beam, is known from WO 01/72518 A1. In this method the energy of the energy beam is introduced either directly or, following a conversion in an absorption layer, indirectly into the print substance. The print substance consists, for example, of a solvent, such as, for example color pigments dissolved in water. In both cases, a small gas bubble is explosively formed in the print substance by heat expansion or evaporation of, in particular, the solvent, as a result of the high energy density of the energy beams. This bubble, in the course of its exit from the print substance, displaces a portion of the print substance in the direction of a material to be imprinted, which material is located at a slight distance from the print substance, and sets a print point there. A so-called light-hydraulic effect is employed in this method, in which a shock wave is generated in a liquid by the light pulse. The light pulse is either directly introduced into the liquid, or acts indirectly on the liquid, and in both cases suddenly leads, in a point-like manner, to a thermally caused volume expansion in the liquid. The light-hydraulic effect is described in greater detail in EP 0 836 939 B1 while citing further sources.
In accordance with the above-mentioned WO 01/72518 A1, the print substance is applied as a homogeneous film to an ink carrier. The ink carrier is embodied, for example, as a rotating cylinder, and preferably is embodied as a transparent hollow cylinder which is made of glass. The ink carrier and the material to be imprinted are moved past each other without touching. If an absorption layer has been applied to the full surface of the ink carrier, the energy beam first penetrates the print substance, which, in this case, is not absorbent for its wavelength, and only then impacts on the absorption layer, which absorption layer converts the energy beam's radiation energy into heat or a pulse transfer. The absorption layer preferably consists of a crystalline material, preferably of poly-silicate. The crystal size of this material lies between 10 nm and 1000 nm and advantageously is less than the wavelength of the radiated energy employed. The thickness of the absorption layer is said to be less than 10 μm, and preferably is less than 1 μm. An energy beam directed to the print substance is said to have an incidence of more than 0° and less than 75°. The distance between the ink carrier and the material to be imprinted, which is moved past it at a conveying speed, is cited to be less than 2 mm, and preferably is even less than 0.5 mm. The pulse length of the energy radiation is said to be less than 1 μs, and is preferably between 100 ns and 200 ns. The output of the energy radiation lies at an order of magnitude of 50 W to 100 W or more. Laser diodes or arrays, i.e. arrangements thereof, are mentioned by way of example as energy sources. Specific information regarding the wavelength and the pulse sequence frequency of the energy radiation used is not present in this prior document.
An ink jet printer is known from DE 37 02 643 A1. Ink is applied in a thin layer of 10 μm to 100 μm to a glass substrate or to an ink ribbon, and points on the substrate or ribbon are heated, for a period of 0.1 μs to 1 μs, to more than 100° C. as a function of a beam of a laser, preferably a CO2-laser, which beam has been modulated by use of an image signal. A bubble is formed which, when it bursts, transfers ink to a material to be imprinted, which material is moved past the glass substrate or the ink ribbon with the heated ink at a short distance of less than 1 mm. In a preferred embodiment, an ink jet printer for use in printing several printing inks, such as, for example, red, green, blue and black commercially available water-soluble ink is described, and wherein an ink cartridge is provided for each printing ink, each of which ink cartridges is sequentially introduced into the beam path of the laser. In connection with printing inks having little light-absorbing properties, such as red ink, or in particular yellow ink for example, a light-absorbing film of a layer thickness of less than 20 μm, which film has been evenly painted on the substrate, is employed, and on which film the light beam of the laser impinges. The light-absorbing film heats the ink which is in contact with it until a bubble is formed. The bubble is then driven out of the ink cartridge in the direction toward the material to be imprinted.
Since print substances of different colors, and therefore also of different material structures, are employed in printing technology, and wherein the print substances, which differ from each other, can be arranged, for example, on different ink carriers in the same printing press, it is desirable for different print substances to be printed by the same printing press in accordance with the printing processes described at the outset.